Canada's Impaired Driving Rose After Legalization — But Enhanced Enforcement May Be Why
Drug-impaired driving incidents in Canada increased 42% above projected trends after 2018 legalization, but the increase was more associated with enhanced police enforcement and pandemic effects than with cannabis sales.
Quick Facts
What This Study Found
Post-2018, police reported 65 extra drug-impaired incidents per million annually (42% above trend) and 280 extra alcohol-impaired incidents per million (17% above trend); increases were associated more with drug recognition expert employment and pandemic restrictions than cannabis sales.
Key Numbers
65 extra drug-impaired incidents/million/year (42% above trend); 280 extra alcohol-impaired incidents/million/year (17%); drug-impaired positively associated with drug expert employment (p<0.05) and cannabis sales (p<0.05).
How They Did This
Interrupted time-series analysis of province-level annual police-reported impaired driving counts (2009-2023), with regressions testing associations with legal cannabis sales, use prevalence, police drug experts, and COVID-19 restrictions.
Why This Research Matters
The headline finding — more impaired driving after legalization — is misleading without context. Enhanced enforcement capacity (more drug recognition experts) detected more cases that previously went unrecorded.
The Bigger Picture
This highlights a fundamental measurement challenge: when you improve detection, reported rates rise even if actual behavior doesn't change — a dynamic policymakers must understand when evaluating legalization outcomes.
What This Study Doesn't Tell Us
Police-reported data reflects enforcement activity, not actual impairment prevalence; cannot distinguish cannabis from other drug impairment in most cases; province-level analysis may mask local variation.
Questions This Raises
- ?What proportion of the increase represents genuinely new impaired driving versus improved detection?
- ?How should impaired driving metrics be adjusted for enforcement capacity changes?
Trust & Context
- Key Stat:
- Evidence Grade:
- Robust interrupted time-series analysis with multiple covariates, but police-reported data inherently reflects enforcement patterns, not just behavior.
- Study Age:
- Published in 2026 with data through 2023, providing 5 years of post-legalization trend data.
- Original Title:
- Police-Reported Impaired Driving After Recreational Cannabis Legalization in Canada.
- Published In:
- American journal of preventive medicine, 70(2), 108176 (2026)
- Authors:
- Armstrong, Michael J(5)
- Database ID:
- RTHC-08089
Evidence Hierarchy
Frequently Asked Questions
Did cannabis legalization increase impaired driving in Canada?
Police reports of drug-impaired driving rose 42% above trend after legalization, but the increase was more strongly associated with enhanced enforcement capacity (more trained officers) than with cannabis sales.
Are more people actually driving high, or are police just catching more?
The data suggests improved detection plays a major role — the hiring of more drug recognition experts was the strongest predictor of increased reports, suggesting many of these cases existed before but went undetected.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-08089APA
Armstrong, Michael J. (2026). Police-Reported Impaired Driving After Recreational Cannabis Legalization in Canada.. American journal of preventive medicine, 70(2), 108176. https://doi.org/10.1016/j.amepre.2025.108176
MLA
Armstrong, Michael J. "Police-Reported Impaired Driving After Recreational Cannabis Legalization in Canada.." American journal of preventive medicine, 2026. https://doi.org/10.1016/j.amepre.2025.108176
RethinkTHC
RethinkTHC Research Database. "Police-Reported Impaired Driving After Recreational Cannabis..." RTHC-08089. Retrieved from https://rethinkthc.com/research/armstrong-2026-policereported-impaired-driving-after
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.